The objective is to improve understanding of the endocrine and para-endocrine functions of the lungs by defining structure-function correlations of the cells that make up the alveolar-capillary unit with particular focus on the role of endothelial cells. We plan to use new techniques of electron microscopy and cell culture in efforts to define the topography of angiotensin converting enzyme at the ultrastructural level, to obtain pure capillary endothelium in culture and to examine for postulated metabolic activities of pulmonary endothelium such as the dehydration of bicarbonate and the inactivation (in terms of platelet aggregation) of adenosine-5' -diphosphate. This aim will include studies to define the cellular and subcellular distribution of carbonic anhydrase, ADPase, aminopeptidase A and kinin converting enzyme.